SEMICONDUCTOR OPTICAL INTEGRATED DEVICE

A device includes: a mesa stripe structure comprising a semiconductor in a stripe shape extending in a first direction, with first and second portions spaced apart in the first direction, and a third portion between the first and second portions; and an electrode pattern including a first electrode overlapping with the first portion but not overlapping with the second portion, and a second electrode overlapping with the second portion but not overlapping with the first portion. The first and second electrodes are separated. The electrode pattern comprises a metal in a shape of not overlapping with the third portion. The electrode pattern includes an adjacent area not overlapping with the mesa stripe structure. The adjacent area is next to the third portion in a second direction orthogonal to the first direction, and is on a semiconductor layer continuous to the mesa stripe structure.